The ultimate goal of this proposal is to desccribe molecular details of the activation of glucose transport by insulin. Recent developments in this area support the hypothesis that hormonal stimulation of glucose transport in the target cells of fat and muscle is a result of the redistribution of transport proteins from a pool inacessible to the cell surface, therefore presumably intracellular, to one present and accessible on the cell surface. This hypothesis is supported by convincing but indirect evidence. Moreover, it appears likely that this process of membrane protein translocation in response to insulin also involves the receptor for insulin-like growth factor 2 (IGF-2). Based on current knowledge of membrane protein movement, it would appear that glucose transporters and IGF-2 receptors reside in intracellular vesicles in the basal state, and these vesicles move to the cell surface in response to insulin. Nothing is known about these putative vesicles at present. Also unknown and uncharacterized are the attending proteins and cellular structures certain to be involved in the movement of vesicles to and from the cell surface (excepting the insulin receptor). Thus the specifi aims of this proposal are to identify, purify and characterize the vesicles and their constituent proteins that move to the cell surface in response to insulin using the rat fat cell system. The protein components to be studied include the glucose transport protein and the IGF-2 receptor. The primary experimental approaches will rely on classical biochemical and cell biological techniques such as chromatography and ultracentrifugal separation of subcellular structures. There is very good reason to suspect however that monoclonal antibody technology can also be exploited to select for and identify those proteins that, like the glucose transporter and the IGF-2 receptor, are differentially expressed at the cell surface due to insulin. These studies should provide information about insulin action on the molecular level, and it is hoped that such information may eventually be applicable in relation to the understanding of diabetes.